This invention relates to an absorbent composite having a fibrous matrix and at least one superabsorbent material. At least one of the superabsorbent materials is capable of swelling during fluid absorption and, by application of a triggering mechanism, deswelling to release and reswelling to absorb at least some of the absorbed fluid. In one embodiment of this invention this swelling, deswelling, and reswelling of the superabsorbent materials is repeatable.
Superabsorbent materials are useful in personal care absorbent articles for absorbing a large amount of fluids. Superabsorbent materials are often combined with water-insoluble fibers to create an absorbent composite for use in an absorbent core of an absorbent article. Recent improvements in absorbent composites have increased fluid intake rates of the absorbent composites complementing the absorbent composite absorbent capacities. However, current absorbent composites useful in absorbent cores of absorbent articles generally have inadequate, or less than desirable, fluid distribution properties. Poor fluid distribution decreases the full utility efficiency of absorbent composites as not all the superabsorbent material is absorbing liquid.
Fluid distribution in an absorbent composite is generally dependent on the amount of free liquid available for distribution, the structure and materials of the absorbent composite, and a time factor. One potential solution known in the art for improving fluid distribution in an absorbent composite is to use superabsorbent materials having a slow absorbency rate. The theory for using slow absorbency superabsorbent materials is that there would be diminished or delayed gel blocking and thereby providing more free liquid and time for the liquid to distribute away from the insult target area. However, although distribution was enhanced using the slow superabsorbent, the absorbent composite typically did not provide necessary leakage protection. The extra free liquid not absorbed quickly by the slow absorbency superabsorbent would leak from the absorbent composite and eventually from the absorbent article.
As can be seen in the use of slow absorbency superabsorbent materials, there is a conflict between the functions of leakage and distribution. One problem with the use of slow swelling rate superabsorbent materials in an absorbent composite is that the time required to lockup liquid into the superabsorbent material is relatively long. It is this free liquid which is believed to be responsible for leakage of liquid from an absorbent product while in use. To reduce leakage, the absorbent composite needs to lockup liquid at a rate similar to the liquid delivery rate. However, if the superabsorbent materials absorb the liquid, then distribution of liquid is reduced since there is no free liquid to be distributed. The inventors have conceived of and demonstrated one way to rectify this conflict. Using superabsorbent materials that have the ability to quickly lockup liquid and then gradually release this liquid so that it can be distributed will result in desirable leakage and distribution behavior.
There is a need for an absorbent composite that has enhanced fluid distribution properties while maintaining enhanced lockup properties, thereby maximizing the absorbent capabilities of superabsorbent materials.
This invention relates to an absorbent composite which utilizes multifunctional superabsorbent materials to enhance distribution of fluids. Current commercial superabsorbents have one single function, to swell and absorb fluids. This invention relates to the use of superabsorbent materials which swell and absorb fluids, and which also can deswell and release fluids into the surrounding composite and towards additional superabsorbent material that is away from an intake area.
The superabsorbent materials of this invention swell during absorption of fluids and, in one embodiment, are triggered to deswell and release fluid by a triggering mechanism. The free liquid released by the triggered deswelling is then free to be distributed away from the target area where the initial insult occurred. Triggering mechanisms include, without limitation, thermal, chemical, mechanical, electronic, magnetic, and radiation energies. In one embodiment of this invention the swelling and deswelling of the superabsorbent materials can be repeated for more than one cycle. Multiple swelling and deswelling cycles allow multiple insults of liquid to be locked up, released, and then distributed throughout an absorbent composite, fully utilizing the absorbent capabilities of the full absorbent composite and minimizing leakage.
One embodiment of this invention relates to an absorbent composite having a combination of swelling/deswelling superabsorbents and superabsorbents that do not deswell. In one embodiment the superabsorbent materials capable of swelling or deswelling are placed in the target area, or the area where the fluid insult is initially applied, and away from the target area is additional superabsorbent materials capable of fast absorption. The swelling/deswelling superabsorbent materials quickly absorb the initial insult and are then triggered to deswell, thereby distributing the absorbed liquid to the superabsorbent material away from the target area. In one embodiment all the superabsorbent material is capable of swelling and deswelling but the trigger is activated only to superabsorbent materials in the target area receiving the first fluid thereby deswelling and distributing the released fluid to the surrounding superabsorbent material which was not triggered.
An additional embodiment of this invention relates to an absorbent composite in which a first superabsorbent material that swells slowly is located in a target area. A second superabsorbent material that is capable of swelling and deswelling is placed just outside the target area of the absorbent composite. A normal or fast swelling rate third superabsorbent material is located in the absorbent composite such that the swelling and deswelling superabsorbent is located between the slow swelling rate superabsorbent and the normal or fast swelling rate superabsorbent.
Further embodiments and advantages of this invention will be described below in the Detailed Description of the Presently Preferred Embodiments.